zdimension 11 hours ago

Did not know that such things could be accomplished by registering a new file coding format. Reminds me of https://pypi.org/project/goto-statement/

  • zahlman 10 hours ago

    This one is arguably even more of a hack; it's working at the source code level rather than the AST level.

    The "coding" here is a bytes-to-text encoding. The Python lexer expects to see character data; you get to insert arbitrary code to convert the bytes to characters (or just use existing schemes the implement standards like UTF-8).

  • crabbone an hour ago

    I think there's a package to treat Jupyter notebooks as source code (so you can import them as modules).

    While the OP package is obviously a joke, the one with notebooks is kind of useful. And, of course, obligatory quote about how languages that don't have meta-programming at the design level will reinvent it, but poorly.

zelphirkalt 10 hours ago

I found dictionary unpacking to be quite useful, when you don't want to mutate things. Code like:

    new_dict = {**old_dict, **update_keys_and_values_dict}
Or even complexer:

    new_dict = {
        **old_dict,
        **{
            key: val
            for key, val in update_keys_and_values_dict
            if key not in some_other_dict
        }
    }
It is quite flexible.
  • peter422 8 hours ago

    I love the union syntax in 3.9+:

      new_dict = old_dict | update_keys_and_values_dict
    • parpfish 8 hours ago

      Don’t forget the in place variant!

        the_dict |= update_keys_and_values_dict
      • masklinn 4 hours ago

        No no, do forget about it: like += for lists, |= mutates “the dict”, which often makes for awkward bugs.

        And like += over list.extend, |= over dict.update is very little gain, and restricts legal locations (augmented assignments are statements, method calls are expressions even if they return "nothing")

qwertox 3 hours ago

This confuses me a bit

  dct = {'a': [1, 2, 3]}
  {'a': [1, *rest]} = dct
  print(rest)  # [2, 3]
Does this mean that i can use?

  dct = {'a': [1, 2, 3]}
  {'b': [4, *rest]} = dct
  print(rest)  # [2, 3]
and more explicit

  dct = {'a': [1, 2, 3]}
  {'_': [_, *rest]} = dct
  print(rest)  # [2, 3]
  • qexat 14 minutes ago

    None of the last two LHSes will match `dct`, so you'll get a runtime error.

agumonkey 5 hours ago

Coming from lisp/haskell I always wanted destructuring but after using it quite a lot in ES6/Typescript, I found it's not always as ergonomic and readable as I thought.

odyssey7 an hour ago

Python needs a better dictionary. Also, Python needs better names for things than dict.

nine_k 10 hours ago

In short, it runs a text preprocessor as the source text decoder (like you would decode from Latin-1 or Shift-JIS to Unicode).

  • agumonkey 5 hours ago

    yeah that's the funny part here, would never have thought of this

nikisweeting 6 hours ago

I would donate $500 to the PSF tomorrow if they added this, the lack of it is daily pain

  • IshKebab 2 hours ago

    You shouldn't be using dicts for data that you know the name of anyway - use dataclasses or named tuples. Dicts are best for things with keys that are not known at compile time.

  • almostgotcaught 6 hours ago

    you can't do this consistently across all cases without compiler assistance (see https://doc.rust-lang.org/book/ch19-03-pattern-syntax.html or https://peps.python.org/pep-0636/#matching-builtin-classes linked below).

    • nikisweeting 5 hours ago

      perfect is enemy of good imo, dict destructuring is so valuable that I'm willing to bend some rules / add some rules to make it possible. can't we just copy whatever JS does?

      • skeledrew 5 hours ago

        If it's that valuable to you personally you can use that project to remove your "daily pain". No need to inflict the pain caused by such a thing being present in official Python. Some of us like for the language to remain highly readable.

      • almostgotcaught 4 hours ago

        > perfect is enemy of good imo

        You can't land a language feature that only sometimes works - that's absolutely horrid UX.

        > can't we just copy whatever JS does?

        I wasn't aware that js does this and I don't know it's implemented. So maybe I should retract my claim about compiler assistance.

  • crabbone an hour ago

    Now come on... for code golf? Why on Earth would anyone want extra syntax in a language with already tons of bloat in the syntax that contribute nothing to language's capabilities? It's, in Bill Gates words, like paying to make airplanes heavier...

    This package is a funny gimmick, to illustrate, probably, unintended consequences of some of the aspects of Python's parser. Using this for anything other than another joke is harmful...

andy99 10 hours ago

  def u(**kwargs):
    return tuple(kwargs.values())
Am I missing something, is this effectively the same?

*I realize the tuple can be omitted here

  • Izkata 9 hours ago

    You have to pull them out by key name, and not just get everything. Here's a working version, though with a totally different syntax (to avoid having to list the keys twice, once as keys and once as resulting variable names):

      >>> def u(locals, dct, keys):
  ...     for k in keys:
  ...         locals[k] = dct[k]
  ... 
  >>> dct = {'greeting': 'hello', 'thing': 'world', 'farewell': 'bye'}
  >>> u(locals(), dct, ['greeting', 'thing'])
  >>> greeting
  'hello'
  >>> thing
  'world'
  >>> farewell
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  NameError: name 'farewell' is not defined
    Modifying locals() is generally frowned upon, as there's no guarantee it'll work. But it does for this example.
  • sischoel 5 hours ago

    Or use itemgetter:

      >>> from operator import itemgetter
  >>> dct = {'greeting': 'hello', 'thing': 'world', 'farewell': 'bye'}
  >>> thing, greeting = itemgetter("thing", "greeting")(dct)
  >>> thing
  'world'
  >>> greeting
  'hello'
    • giingyui an hour ago

      There are so many things like this one in the standard library that it kinda pisses me off when I discover a new one.

  • Grikbdl 9 hours ago

    Yours relies on ordering, OP's presumably does not.

  • masklinn 4 hours ago

    TFA looks things up by key, and allows pulling a subset of the dict.